PMID 35193705

Research
All papers

Hybrid high-intensity interval training using functional electrical stimulation leg cycling and arm ski ergometer for people with spinal cord injuries: a feasibility study

Vestergaard M, Jensen K, Juul-Kristensen B

Question

Can a hybrid 4 x 4-minute HIIT protocol using FES leg cycling plus arm ski ergometer be delivered safely and feasibly to people with SCI paraplegia before a future randomized trial?

Summary

This uncontrolled feasibility study tested whether adults with stable spinal cord injury paraplegia could safely complete an 8-week hybrid HIIT program combining functional electrical stimulation leg cycling with arm ski-ergometer exercise. No serious adverse events occurred, attendance averaged 82% of prescribed training minutes, and participants gave positive feedback, but fewer than 60% reached the intended 90% peak-watt intensity target.

Methodology

  • Eight outpatients with stable SCI paraplegia, mean 14.5 years since injury, mostly men and manual wheelchair users.
  • 8 participants.
  • Seated FES leg cycling plus arm ski ergometer double-poling.
  • Work intervals: 4 minutes.
  • Recovery: 2 minutes active rest at warm-up pace.
  • Intensity: Target 90% peak watts for arms and legs; actual mean 92% on FES cycle and 82% on SkiErg.
  • Approximately 32 minutes structured time.
  • 3 sessions per week.
  • 8 weeks.
  • Non-randomized pre-post feasibility study
  • Adverse events, Participant acceptability, Shoulder pain, and Training intensity were tracked.

Outcomes

Safety

No serious adverse events occurred; minor symptoms included headaches, pain, dizziness, increased spasms, and vomiting.

Descriptive feasibility result; 0 incidents of autonomic hyperreflexia and 0 acute cardiac events in progression criteria.

Improved

Training intensity

Mean achieved intensity was high on the FES cycle and lower on the SkiErg, but the protocol failed the predefined criterion that at least 60% of participants reach 90% peak watts.

Mean 92% (SD 18.9) peak watts for FES cycle and 82% (SD 10.3) for SkiErg; 43% reached 90% on FES and 14% on SkiErg.

Mixed

Attendance and dropout

Attendance was acceptable on average but variable, with one dropout due to back pain.

Mean attendance 82% of prescribed training minutes; dropout 12.5%.

Mixed

VO2peak

Mean VO2peak increased after the 8-week program.

1.64 (SD 0.39) to 1.91 (SD 0.61) l/min; 18.25 (SD 2.82) to 21.21 (SD 5.62) ml/kg/min; 17% (SD 17.47) increase.

Improved

Participant experience

All participants reported a positive experience with training.

Progression criteria reported 1 participant rating experience during/after training higher than 3 on a 1-7 scale where 1 was most acceptable.

Improved

Insights

  • Clinical HIIT protocols for SCI need explicit medical screening, symptom monitoring, and individualized intensity adjustment.
  • Objective peak-watt targets may be unreliable if test protocols are not standardized or if participants are unfamiliar with maximal testing.
  • A 4 x 4-minute long-interval format may be feasible in supervised SCI rehabilitation, but target intensity or recovery length may need modification.
  • Equipment setup and transportation/secondary health issues can materially affect adherence.

Limitations

  • Small sample size
  • No control group
  • No blinding
  • Feasibility design not powered for efficacy
  • Potential selection bias toward motivated participants
  • Hybrid VO2peak and peak-watt test validity and reliability unknown
  • Feasibility criteria were pragmatically set

Safety

  • No serious adverse events occurred.
  • Two participants experienced mild headache after training without other signs of autonomic hyperreflexia.
  • Minor adverse effects included neck pain, arm/shoulder pain, dizziness, increased spasms, and vomiting.
  • One participant dropped out after 6 weeks due to back pain.
  • Authors emphasized pre-screening for cardiac health risks and autonomic hyperreflexia.